X-ray imaging is a well known and extremely valuable tool for the early detection and diagnosis of various disease states in the human body. The use of contrast agents for image enhancement in medical x-ray imaging procedures is widespread. An excellent background on iodinated and other contrast agents for medical imaging is provided by D. P. Swanson et al, Pharmaceuticals in Medical Imaging, 1990, MacMillan Publishing Company.
Various soluble and water insoluble iodinated amides and esters have been used as x-ray contrast agents. For example, U.S. Pat. No. 3,097,228 describes derivatives of 2,4,6-triiodobenzoyloxyalkanoic acids having the structure ##STR2## wherein R.sup.1 is H or lower alkyl, R.sup.2 is H or alkanoyl, R.sup.3 is H or alkanoylamino, and R.sup.4 is lower alkyl.
U.S. Pat. No. 3,144,479 describes iodinated benzoic acid esters having the formula ##STR3## wherein X is an iodine atom or an amino group and R is selected from H, alkyl, alkoxyalkyl, i.e., --CH.sub.2 --.sub.m --O--R", wherein R" is alkyl and m is 1 or 2, phenyl and a particular iodinated aromatic group.
However, these references do not disclose or suggest compounds featuring an aromatic group linked through an alkylene group to an ester group on an iodinated aromatic ring.
EP-A 498,482 describes nanoparticulate x-ray contrast compositions which have proven to be extremely useful in medical imaging. However, particulate contrast agents in certain in vivo applications can exhibit less than fully satisfactory enzymatic degradability, e.g., in lymph fluids, plasma or blood.
It would be desirable to provide compounds for use as x-ray contrast agents having improved enzymatic degradability and appropriate solubility profiles.